CEREBRAL WHITE MATTER INSULT CORRELATES WITH BLOOD PRESSURE VARIABILITY

Abstract Ref: 
0306

Dan Ryan1, Soren Christensen2, Rose Anne Kenny1, James F Meaney3, Ruth McDonagh1,
Hassan Haswadi1, Georgia Richard1, Joseph A Harbison1
1Geriatrics Department, St. James’s Hospital, Dublin, Ireland
2Stanford University, California, USA
3Centre of Advanced Medical Imaging, St. James’s Hospital, Dublin, Ireland

Background: Cerebral associations with blood pressure variability (BPV) include incident
stroke and white matter disease, however, it is unclear whether these are associations
or manifestations of BPV. We explored a causal relationship by interrogating regions of
the brain susceptible to sudden fluctuations in BP, known as borderzone regions, in
patients with high BPV.
Methods: Cases were compared with age and gender-matched controls using standard
deviation (SD) of daytime systolic blood pressure (BP) from ambulatory 24-hr BP readings,
and dichotomised based on values greater than or less than 22 mmHg. All underwent
Diffusion Tensor MRI with interrogation of one white matter borderzone region
(centrum semiovale) and of two white matter non-borderzone regions (internal and external
capsule) according to fractional anisotropy (FA) values, which reflect white matter
integrity.
Results: Forty-six patients were recruited in 1:1 case-control ratio. The mean age was
68.5 years (SD 10.8) and 22 (48%) were female. The mean SD of systolic BP in cases
and controls was 27 mmHg and 17 mmHg respectively. Use of anti-hypertensive medication
and the prevalence of stroke and diabetes was similar in both groups. The integrity
of borderzone white matter region was significantly more damaged in cases than in controls;
FA values 0.43 (SD 0.06) and 0.47 (SD 0.03) respectively, p = 0.01. Conversely one
non-borderzone white matter region was more intact in cases than in controls and in the
other both were equally intact; internal capsule FA in cases 0.54 (SD 0.05) and in controls
0.51 (SD 0.05), p = 0.03; External capsule FA in cases 0.41 (SD 0.04) and in controls 0.4
(SD 0.05), p = 0.44.
Conclusion: High BPV correlates with selective insult to regions of the brain vulnerable
to flow change. Consequently BPV may directly damage white matter tracts, which may
manifest clinically as vascular cognitive impairment, gait disorders and possibly incident
lacunar stroke.